Platen rollers are commonly used in linear or serial printing to provide a firm foundation for various forms of print heads. In thermal printers, platen rollers are used for squeezing print media against a thermal print head to provide proper thermal conduction between the print head and media. Platen rollers can also allow accurate movement of print media due to minimal friction characteristics. Certain types of thermal print heads are restricted to using a maximum radius platen roller, thus requiring a certain roller wrap and curvature to the print media.
The use of rotating platen rollers in conjunction with thermal print heads presents considerable alignment, manufacturing and cost considerations. The development of thermal printers has typically included the use of platen rollers having a deformable rubber coating. Such platen rollers are used to pressure print media against integrated circuit, thermal print heads for providing sufficient thermal contact and heat transfer to the print media. The rubber surface of the platen roller deforms when the roller is pressing the print media against the thermal print head. With such platen rollers more energy may be needed to obtain the same optical density in the printed image when the thermal element in the print head does not conform to the shape of the platen roller surface when they are in contact with each other.
During rotation all imperfections related to rubber rollers such as eccentricity, roundness, circumferential and longitudinal stiffness variations, bearing imperfections, etc. are detrimental to printed image quality.
As the state of the art in thermal printers advances and efforts are made to provide new thermal printers that can meet new performance requirements and substantially reduce or eliminate some of the undesirable characteristics of the known thermal printers, it would be advantageous to have a thermal printer which does not require a rotating platen roller.